Approximately 80-90% of human cerebral ischemic events are caused by thromboembolism. There is a compelling need to develop acute therapeutic interventions for the treatment of stroke. We present preliminary data indicating that atorvastatin, a hydroxymethylglutaryl coenzyme A reductase inhibitor, extends the therapeutic window of thrombolysis in a rat model of embolic stroke by activation of the PI3- K/Akt signaling pathway. However, the atorvastatin mediated therapeutic effect is independent of eNOS and lipid levels. The goals of this application are to determine the efficacy of statins in combination with thrombolysis for treatment of acute ischemic stroke and to investigate mechanisms underlying the therapeutic effects of atorvastatin as an adjuvant agent to recombinant human tissue plasminogen activator (rht-PA). Our hypotheses are: 1) Treatment of stroke with atorvastatin in combination with rht-PA extends the therapeutic window for acute stroke;2) Atorvastatin activates the PI3-K/Akt signaling transduction pathway in cerebral endothelial cells, which decreases cerebral microvascular thrombosis and blood brain barrier (BBB) leakage by negatively regulating endothelial cell genes that promote thrombogenicity, vascular permeability, and inflammation;3) Activation of the PI3-K/Akt cell survival pathway in neurons by atorvastatin attenuates ischemic neuronal damage exacerbated by delayed treatment of rht-PA. The proposed experiments have been designed to test these hypotheses. Using Magnetic Resonance Imaging (MRI) and 3D laser scanning confocal microscopy (LSCM) techniques, we will first investigate the effects of short-term, high-dose atorvastatin on cerebral vascular patency and integrity including cerebral blood flow (CBF) and BBB leakage, and the neurotoxic effects of tPA. Using laser capture microdissection in combination with real time PCR, Western blot analysis and specific inhibitors which block PI3-K/Akt activation, we will then delve into the mechanisms by which the PI3K/Akt signaling pathway mediates expression of endothelial cell genes involved in thrombosis and BBB leakage, and expression of neuronal genes engaged in the neurotoxic effects of tPA. These studies will lead to a comprehensive understanding of mechanisms underlying the therapeutic effects of statins on extending the window of thrombolysis for acute ischemic stroke and may provide a novel and useful treatment strategy for human ischemic stroke.